[s-cars] Found 10 PSI Fuel Pressure and .8 Volts

[Cody Payne]

Hey Sean,
	Thanks for your data.  

At idle w/ vac I am at 62 PSI.  Under WOT around 5200 RPM my boost gauge
reads around 25 PSI...so I should see 87 PSI on my fuel gauge..but only
seeing ~70 PSI now vs. ~60 PSI before the new relay.

So I am still short ~17 PSI.  So really the difference between my test,
is that my injectors are running high duty as well as the loads on the
alternator.  I would expect that your expected and actual pressures
would be slightly different due to those 2 variables...but I could be
wrong?

Cheers

cp



-----Original Message-----
From: Sean Douglas [mailto:quattro20v at telus.net] 
Sent: Sunday, November 06, 2005 8:41 PM
To: Cody Payne; 'Dave Forgie'; s-car-list at audifans.com
Subject: RE: [s-cars] Found 10 PSI Fuel Pressure and .8 Volts

Cody:

When you measured your fuel pressure at WOT, what manifold pressure are
you seeing? I only ask because the fuel pressure is dependent on the
manifold pressure and is controlled by the fuel pressure regulator.

I did this last year, but did the test differently. After relaying the
fuel pump as per Dave Forgie's instructions, I put a pressure gauge
inline on the supply line, manually jumped the fuel pump so it was on
(engine off) and disconnected the vacuum / boost line to the fuel
pressure regulator and pressurized this with regulated compressed air.
Starting at 0 PSI and going up in various steps to 28 PSI, my results
were:


0 PSI, 57 PSI
10, 65
15, 70
20, 75
22, 77
25, 79
28, 83

By my calculations, I was 4-5% below the target fuel pressure across all
values. The voltage at the pump was 12.4 volts, perhaps when the engine
is running, the voltage will go up and hence the fuel pressure.

The reason I did all this testing was because with the RS2 mods, I was
running lean (pinging) and wanted to see if I had enough fuel pressure.
In the end I decided it was a software issue and switched software (to
Dahlback) and now the pinging is 99% gone.

Sean Douglas

> -----Original Message-----
> From: s-car-list-bounces at audifans.com 
> [mailto:s-car-list-bounces at audifans.com] On Behalf Of Cody Payne
> Sent: Sunday, November 06, 2005 6:21 PM
> To: Dave Forgie; s-car-list at audifans.com
> Subject: Re: [s-cars] Found 10 PSI Fuel Pressure and .8 Volts
> 
> 
> For those who have a fuel pressure gauge on their cars...what sort of 
> pressure have you seen from your stock fuel pump?
> Can you get 86+ PSI WOT?
> 
> Granted the set-up I had today was great as I could drive and view the

> fuel pressure gauge mounted on the hood.  But on the dyno works great 
> too ;)
> 
> My stock fuel pump is about 3 years old.
> 
> Thx
> 
> cp
> 
> -----Original Message-----
> From: s-car-list-bounces at audifans.com 
> [mailto:s-car-list-bounces at audifans.com] On > Behalf Of Dave Forgie
> Sent: Sunday, November 06, 2005 7:10 PM
> To: s-car-list at audifans.com
> Subject: [s-cars] Found 10 PSI Fuel Pressure and .8 Volts
> 
> You're welcome Cody.  But at 70 psi you are still down at least 16 psi

> from the minimum 86 psi you need at 28 psi relative boost  (58 psi (4
> bar) plus 28 psi boost).  I suspect that your 091G is got a problem 
> -either its weak or its inlet is clogged.
> 
> Dave F.
> 
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